Science of Youth
by Duochanfan
Summary: Sherlock and John are on a case when they come across the same device that has killed five men. This time, the results aren't death but exactly what the mad scientist wanted all along, Youth. Now they just have to find a way to get back to normal, are Greg and Mycroft up to watching over them? De-aged Sherlock and John, Parental Greg and Mycroft, No Slash.
1. Chapter 1

**I don not own BBC Sherlock, they are the creative works of Steven Moffat, Mark Gatiss and of course the wonderful Sir Arthur Conan Doyle.**

**Well, I do hope you like this one. It hasn't been beta read, as I am still looking for one for this one. If you want to beta this, or my other Sherlock Fic, please PM me.**

**There is no slash in this fic at all, its all family and friendship. I do hope you all enjoy it!**

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**The Science of Youth**

**Prologue**

Sherlock and John ran into the warehouse. They went thought several rooms and corridors but were soon stood in the middle of a large room that they had chased a scientist by the name of Dominic Underwood. The forty-eight year old man that had been going around experimenting on the unsuspecting people of London. So far none of the so-called effects from the gasses had been good, and five people had died as a result of this mad scientists attempts at eternal youth. The two looked around the room; Underwood was nowhere to be found. Standing innocently in the middle of the room was a small device, no larger than the skull that normally sat on the fireplace back at Baker Street. The two men looked at one another, the device was exactly the same as the ones that had been found at the crime scenes.

"Sherlock, I think we need to wait for Lestrade to arrive, he said he would be here in a few minutes. That if we see anything strange or like what was at the scenes we should leave it all alone and take a step back," John told Sherlock, hoping that the other would listen for once.

Sherlock glanced over to John with an almost pleading look in his eyes as he spoke with a slight whine, "John, we lose valuable clues by waiting, and we don't want this killer to get away just because we waited, do you?" it was the way that Sherlock said those words that caused John to cave once again to the younger mans wishes. The Ex Army Doctor really needed to better learn how to resist his flatmate.

"Fine, but if you notice anything that looks like it might set something off, then move your arse away from it and don't touch anything else." He spoke sternly, getting a smile from the other as the two of them walked a little closer to the device in the middle of the room.

Sherlock looked at it carefully as he walked around it slowly. Looking at it from every angle that he could, taking in as much data as he could about it all. His pocket magnifying glass came out and he leaned in even more. The device gave a soft beep that John heard and he went on high alert, he knew that something was going to happen and he moved quickly, hoping to protect Sherlock at least. Something on the device flipped open, as John reached Sherlock and grabbed him. The consulting detective was too absorbed in examining the device to notice what was going on around him. John pulled him away and covered him with his body. Hoping to keep Sherlock away from the gas that was now being released.

The green gas enveloped the two of them completely, both of them held their breath for as long as they could, hoping that the gas would dissipate quickly. Seconds later John began to feel dizzy as he then collapsed on top of Sherlock. The younger man felt the increase of weight on top of him; he turned his head and frowned when he saw something weird. It didn't last long as his eyesight went blurry as he too blacked out.

XxXxX

Lestrade shook his head as he got out of his car, he already knew that Sherlock and John would have gone inside the warehouse, even though he had told them not to. He knew that John would always follow Sherlock, and Sherlock was the one that would ignore him, often dragging him into some sort of trouble. He walked into the warehouse warily, not sure what he would come across, he was a little worried as well since he wasn't getting any answer from the two of them, he had tried calling them a few times as he headed out to them and John always answered his phone. He walked further inside and came to one of the central rooms, in the middle of the room was a small device, and he knew by the sight of it that something bad had happened. It was open and he shuddered, it looked like all the others. It only became more apparent by the large bundle of clothing that was near it. He could see Sherlock's coat as well as John's, and the clothing that the two had been wearing. He slowly moved over to the clothing as it began to move slightly.

A child, looking to be around seven years old came out from underneath the pile first. A mop of curly brown hair and steel grey eyes told the detective the identity of the young one. He wondered a little if the same thing had happened to John. A part of him didn't even find it weird that they could both be kids, instead of their normal adult selves, being around Sherlock for too long soon made the extraordinary feel ordinary.

"Come on John," came the higher pitch of the childs voice as he knelt. He would have been naked, if it wasn't for the overly large plum shirt that was now hanging off his thin frame.

"Coming," a returning voice came back from the bundle as it moved a little more and a jumper-clad toddler came out. The short messy blond hair and baby blue eyes told Lestrade that the younger child was John.

With a shake of his head, he quickly ran over to them, "Sherlock, John?" he questioned, his voice filling with worry, wondering if the two of them were actually all right. He knelt down beside them as the two of them looked up to him.

"Lessphard," John lisped, then frowned as he heard his own voice, "Bugger, phought I goths rid oph phaths," he huffed, annoyed.

Lestrade frowned at him and automatically said, "John, language."

Sherlock looked at the Detective Inspector as he said, not concerned that his voice was now higher than normal, "Lestrade, just because we look like kids, it doesn't mean that our minds are that of children, so please don't insult our intelligence." John grinned a little at that remark, though it hadn't really sank in for the de-aged doctor, that the two of them were actually children now.

Lestrade couldn't help but say, "Sorry, but you two look like little kids at the moment, and John, sorry buddy but you actually look like a toddler." A slight smile on his face as he looked to the younger of the two.

John growled a little, but all Lestrade wanted to do when he heard it, was laugh at how cute it sounded. "I'm phive, I've alwaysss been phmall phor my age." He told him, once again annoyed at his genes that left him smaller than those around him. He was still a little smaller than most, even when he was an adult.

Lestrade shook his head in disbelief, "I thought you might be around three, and how old are you Sherlock?" he asked as he turned to looked at the young genius.

The older kid looked from the almost pouting John to the Detective Inspector, "I'm seven," he answered simply.

Lestrade nodded, he had thought that for Sherlock, but wanted to be sure. He turned back to John and smiled as bright blue eyes were looking up at him, "Right, I have a feeling that we should get the two of you somewhere safe. I don't think either of you want the general public and some of my Yarder's to see you like this."

John nodded his head as he spoke quietly, "Phat would be bessths." It could be a problem if the wrong people got hold of the information that they were vulnerable.

Sherlock nodded as he grimaced, an unpleasant thought coming to his mind, "I really, and I truly mean this, really hate the thought, but I believe that we may have to rely on Mycroft for help on this. He has resources we don't." He sighed in annoyance as he muttered under his breath, "Let's hope he doesn't enjoy it too much."

John and Lestrade looked to him in confusion, as John piped up, his voice high and almost squeaky as he asked, "Why do you phay phaths?"

Sherlock looked to him and answered quietly, "When I was little, Mycroft had a habit of always trying to pick me up and cuddle me. He is a nurturer, and since he is twelve years older than me, he did it as often as he could, not that I minded when I was very young. He just didn't stop until I told him to leave me alone and he went off to university, when I was around seven. Let's hope he doesn't try it again or this time his umbrella will end up in a better place." He threatened with a growl, which Lestrade thought was just as cute as John's.

Lestrade was just about able to keep a straight face as he said, "I'll give your brother a call and tell him what's going on."

Sherlock looked to him and asked him, "And how did you get his number?"

Lestrade chuckled at that, "Your brother gave it to me ages ago, and when ever it changes he always sends me the new one. Just in case something happens while you are with me and he needs to be informed."

"I don't like that." Sherlock pouted, not liking the fact that Lestrade and Mycroft kept in touch about him and what he was up to.

"Anyway," Lestrade said, making sure that Sherlock didn't go on a rant about his brother, "Why don't you boys go and get the coats, I can see that you're both cold. So wrap up warm for a bit." He said as he stood up and went to one side, glad that he hadn't brought Donovan with him, who knew what she would have done seeing the two of them like that, she didn't exactly come across as kind where Sherlock was concerned.

Sherlock watched as Lestrade walked away and then turned to John. He could see that John was shivering a little, it was the middle of December, and Christmas was just over a week away. He went over to the bundle of their now, too big clothing, and pulled his heavy coat from the pile.

"Come here John," he coaxed gently, as the smaller child moved over to him and Sherlock wrapped the coat around the two of them and then sat them down on the pile of cloths. He frowned when he could still feel John shivering and wondered if the younger boy was actually going into shock after he had thought about their unusual situation and let it actually since in a little.

"Phanksss," he lisped as he tried to get warm, but couldn't, cuddling a little bit closer to Sherlock.

Sherlock wrapped his arms around him even tighter and pulled him as close as he could, until the younger boy was sat on his lap. He pulled the thick coat closer around him as he said softly, with a little worry in his high voice, "It's all right John," he murmured as he hoped it would help John feel better, not sure what he should do in this type of situation.

Lestrade walked back over and frowned as he saw the worried look on Sherlock's face, "Everything all right boys?" he asked as he knelt down in front of them.

Sherlock looked up and turned worried eyes to him and said softly, "I think John might be in shock. He can't seem to get warm."

Lestrade turned to look down at the small blond, Sherlock opened the coat and stepped out of it, grabbing John's smaller coat to keep himself warm, it wasn't as thick as his own, but it would do. Lestrade smiled to Sherlock as he said, "Let's get the two of you out of here and to somewhere warmer, your brother is bringing a car. He'll be in it and driving. He's also bringing some of his people with him to take care of things.

"I don't know if I would trust my brother to drive," Sherlock murmured to himself.

Sherlock then watched as Lestrade picked John up and settled him in his arms, cradling him like a baby, "You all right John?" he asked softly as he made sure to wrap the tiny doctor up in Sherlock's thick coat.

John couldn't help it as he snuggled closer to Lestrade as he mumbled a little before he answered, "I'm phine." His voice was quiet and sounded tired as he spoke.

Lestrade rolled his eyes as John yawned a little, his bright blue eyes closing a little more each time he blinked. Greg and Sherlock walked out of the building and stepped towards the first black car that had pulled up. Anthea holding the door open and taking the Lestrade's car keys from him, as two more cars pulled up behind it, and more people getting out. Anthea nodded to them and then went into the building, the others following her. The Detective Inspector settled the now sleeping John into the car seat that was installed and made sure that Sherlock was secured in his as well, then got in the front with Mycroft, who soon had them speeding away from the warehouse and towards his home.

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**I have gone through this three times, and I have no doubt that there are still mistakes that remain. I apologise for it, and for those that tell me to get a beta, I am trying. I've just not found one, so if you wish to beta it for me, then please PM me!**


	2. Chapter 2

**I don not own BBC Sherlock, they are the creative works of Steven Moffat, Mark Gatiss and of course the wonderful Sir Arthur Conan Doyle.**

**Here is chapter two. I do hope you all enjoy this. I will be trying to update once a week for this one now.**

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**The Science of Youth**

**Chapter Two**

Mycroft parked the car into the driveway of his two-story home. He had already taken care of his cook and the maid that would come in every other day to clean, making sure that there would be no one around. He looked into the mirror, glancing at the backseats. John was beginning to wake up, yawning cutely. Sherlock was looking moodily out of the window. Mycroft could remember the first time that Sherlock had turned seven; he had started to distance himself from him. His intelligence already scaring other children away, and their parents. Their parents had loved them, but Sherlock had driven them away with his constant need to know things. They couldn't understand him and had left him alone more often than not, neglecting him. Though Mycroft thought things were better between his parents and younger brother now, since they were talking.

"Inspector, please bring Sherlock inside. Even though he will protest, do carry him. I'd rather not let him hurt his feet by walking inside," Mycroft said as he got out of his car and over to John's side, he opened the door and undid the buckles, picking the young child up and settling him in the crook of his arm.

John opened bright blue eyes and looked up into the calm face of his best friends brother, "Mycrophths," he yawned a little as he was picked up. John shivered as the cold air hit him and he snuggled deeper into Mycroft's arms, seeking out his warmth.

Lestrade opened the door for Sherlock and caught the young kid as he tried to jump out of the car. "Sorry kid, I'm carrying you inside. Don't want to let you get hurt just by walking into the house." He told the kid as he swung him up and settled him against his hip; Sherlock was light, though he could see why the kid was thin.

"Lestrade, I am quiet capable of walking from the car and into my brothers house." Sherlock told the man as he tried to get down, almost making Lestrade lose his grip.

Lestrade shook his head; "Not happening little buddy, if I set you down you could hurt your feet. Since they are bare you can easily step on something sharp." He explained to the genius, "I know you want your independence, but you have to be patient. I know it's not something that you have a lot of practice with. Just you wait, you'll be back to normal, solving crimes and running around the streets of London soon enough." Lestrade told him softly as he followed Mycroft into the house, going through the house till they reached a warm living room.

Mycroft looked to the child that was in his arms, slowly waking up. He sat down on the couch and settled John in his lap, letting the child becoming aware of his surroundings slowly. Mycroft couldn't believe how small John was, the detective had told him that the child was five, but he looked a lot younger, around three. He looked over to Sherlock who was now settled on one of the chairs, Lestrade sitting on the one next to it. Mycroft felt John begin to struggle a little, so he loosened his hold on the young one.

John was now wide awake and felt a little uncomfortable, waking up lying in Mycroft's lap. He moved off and settled beside him, leaving behind Sherlock's heavy coat. The large jumper that he was still wearing almost swallowing John whole. He looked around the large room, it was grey and white, tastefully done, with a large TV across from him, a coffee table between the TV and sofa, a bookcase was on one wall, a fireplace not to far from it.

"So, would one of you like to explain what exactly happened and what led up to this little predicament?" Mycroft asked he looked to them in turn, including the Detective Inspector in the question, as he knew that Sherlock had been working a case with the older male.

"Sherlock and John have been helping me on the Underwood Case, Dominic Underwood has been setting off small devices loaded with different combination of gasses. So far he has killed five. Sherlock had figured something out. I don't know what," Lestrade said as he looked over to Sherlock, hoping he might be able to enlighten him to what had drew the two to the warehouse.

Sherlock got the hint and answered the unasked question, "looking at the fourth device I was able to scrap off some residue from something. It didn't belong to the gas that had once been inside of it. It was that, which led me to the warehouse. When we got here there was another device. We had followed Underwood inside, but he was nowhere to be found. I was looking at the device and moments later John had me on the ground away from it. I believe that is why he turned out to be younger than I, since he had gotten most of it on him. The gas was around us before John could get us far enough away. John succumbed to it first. I was able to get a look at him before; I too succumbed to the gas. It looked like there was something under his skin, like it was eating it from the inside," he described graphically.

John couldn't help a shiver of revulsion as he listened to what had happened to him after he had passed out. Mycroft felt it and placed a calming hand on his head and admonished his brother, "Sherlock, less on the descriptions," giving him a pointed look.

Sherlock looked to him and then to John, giving a slight nod, "Next thing I know both John and I are children, the gas this time did not have the same deadly effect it had on the other victims, I can only surmise that the experiment he was conducting was a success."

"And I would say that we need him to get you back to normal," Mycroft realised, getting a nod of agreement from his younger brother.

"So what do we do in the mean time?" Lestrade asked as he looked from one kid to the other.

Mycroft looked at them and said softly, "Well, they will have to live here until we can get this all sorted out."

"No," Sherlock said with a vigorous shake of his head, "I refuse, we can easily stay at Baker Street." He protested, though John remained quiet through it all, which worried the other three in the room slightly.

"Sherlock, while I know that you are independent and have been for a long time, this would not be a good way to show it at the moment. You look like a child, your mind maybe that of an adult, but there will be things you and John will not be able to do. Especially since John is so much smaller," Mycroft argued back, hoping he would be able to get his point across.

"Mycroft, I do not wish to be here," Sherlock said quietly.

"I know little brother, but for now it is the best place for you both." He said as he then added, "Anthea is also going out to get a few items of clothing and something for you both to do. They should be here soon," he frowned as he felt another shiver from John. He looked down at the small child and quickly got up and left the room.

Lestrade and Sherlock watched him go, wondering what was going on. They looked towards John and frowned, he was still pale and shivering once again. Lestrade got up and walked over to him quickly, "John, are you all right?" he asked as Sherlock joined him.

John sent wide blue eyes towards them and nodded, "Yesss," he lisped, though the answer was hesitant and the eyes slightly unfocused.

"I believe that he is still in shock," came Mycroft's voice as he walked back into the room and over to the group. In his arms was a large fluffy blanket, he knelt down and looked to John, "John, you know you're in shock, so don't fight me all right." He said softly, making Lestrade look at him, he had never heard that soft tone come from the man before. Sherlock had, though not in a very long time.

John nodded slowly, wondering what the other was going to do. His mind still not fully comprehending all that was going on around him. Mycroft opened the blanket a little, picked John up and placed him in the middle of it before he soon swaddled and cocooned him inside of it. John felt himself being picked up again as he was soon settled in Mycroft's arms; he blinked slowly as he looked up into the concerned eyes above him.

Mycroft settled back on the sofa as he turned to the other two, "Go and sit down, no need to gawk." He told them as he slowly and gentle began to rock John, hoping that it would help a little.

"Fhankss," John murmured as he moved around a little and settled down. He already felt better, he felt safe and he couldn't help but snuggle closer.

Sherlock watched and came to a different conclusion, "I don't think John is fully in shock, I think part of it is he is behaving like a small child. He is in an environment that is unfamiliar, with people that his childs mind does not recognise. I think that our behaviour may be more child like. Even though our minds are that of our adult selves. I would say that we will behave more as our physical ages at times, and not our mental ages." He said as he looked to his brother.

"Why do you say that?" Lestrade ask him as he looked over to the now seven-year-old consulting detective.

"Because I am fighting, with everything that I am, not to climb the bookcase," he said, almost pouting as he looked over to the Inspector.

Lestrade looked confused and wondered what that was all about as he asked, "And why would you know because of that?"

It was Mycroft that answered him, "Sherlock was always climbing things when he was a child, he stopped around nine. But when he was caught, his excuse was that they were asking to be climbed by being so tall." He smiled fondly, remembering finding Sherlock on top of bookcases and wardrobes more often than not.

John giggled from inside his cocoon, "Mights be why he likesss pho run over roofth topsss."

Lestrade looked to the kid as Mycroft moved him around a little so he would be able to see what was going on. Lestrade soon started laughing, Mycroft nodding at the thought, and began to chuckle as well.

Sherlock looked deep in thought as he said, "you might be right John," and then he too joined the laughter. The three could hear as John continued to giggle, feeling a little relief that he was more like himself.

The door to the room opened and Anthea walked in. The laughter tapered off quickly as she set down a number of bags next to her boss and said, "I got clothes for the two of them. I understood that John is smaller than most so I got clothing that would fit him. I also got a few toys and things that they can play with and do." She paused for a moment and then continued, "We are investigating and looked for Underwood. I have the men searching for him, we hope to have him in custody soon."

"Very good Anthea, thank you." Mycroft said with a please little smile, "You may leave." She nodded back and then left the room.

"Pyjamas I think," Lestrade said as he looked to the time, it wasn't that late, only just gone seven in the evening, but he had no doubt that the two kids would be tired. He knew that Sherlock hadn't had any sleep in almost four days, and John hadn't slept the night before.

"Good idea, lets see what she got," Mycroft said as he moved John around and looked in a few of the bags. Sherlock jumped up and joined him, pulling things out. It didn't take long for almost half the bags to be empty and scattered around the seven year old.

"Got mine," he said gleefully as he went to the other side of the room and quickly changed.

Mycroft pulled out a set of light blue pyjamas that were small enough for John to wear, "Right, let's get you into something more comfortable." He said gently as he unwrapped John from the cocoon he had been in.

John tried to move away as Mycroft reached for the jumper that still swamped his small body, "I can do iths myssselphs." He protested as he tried to grab the clothing off Mycroft.

"All right, but I think you might need help getting that jumper off," he told him softly as he let the child take the clothes from him.

John titled his head to the side and nodded, he would need help with that, "Okay," he agreed as Mycroft helped him pull off the jumper and the thin green t-shirt he had underneath. John shivered a little, as he was now naked; he pulled on the trousers and then the top, feeling only a little warmer. He blushed as his stomach gave a growl, "Sssorry." He lisped out as his face became warmer.

Mycroft chuckled a little as he smiled, "I believe you both should have some food and then an early night. And before the two of you protest that you're all right to stay awake. I think it would be best to get a good night sleep. Your bodies are that of children, and they need rest. So food and then bed." He told them, making sure he got his point across without the two of them protesting.

The two nodded as Lestrade stood up and said, "Well then, I think I'll take my leave of the lot of you and head home." He smiled as Sherlock quickly jumped up and ran over to him, grabbing his hand.

"Please, I would rather you stayed. There is enough room here for all of use, isn't there Mycroft?" he said as he sent a pleading look towards his brother, hoping he would help convinced the Detective Inspector to remain.

Mycroft nodded his head and turned to Lestrade, "Please stay, I believe that they would be more comfortable with you here as well as I." He told him honestly.

"All right, it's not like there is anyone waiting for me at home." He smiled a little.

"Good," Sherlock nodded as John climbed down from the couch where he had been sat and went to join Sherlock as he looked up to the man.

"Would phrepher iphs you phssayed," John said softly. Sherlock using one hand to hold Lestrade's hand and the other joining up with John's as the two of them stood side by side.

Lestrade looked down at him and said, "Don't worry, I will. I can see that this is going to be hard on the two of you and I promise to help all I can."

The two kids nodded, believing in Lestrade and that he would do as he promised. It was something he did with all the victims of crime that he came across, doing his best to help them get the justice that they deserved. John blushed once more as his stomach rumbled, he looked to Sherlock, wondering if he was hungry yet.

"Right, let's make dinner and then get you two settled down for bed." Mycroft said as he looked to the two children, as they were about to rush out of the room, eager to explore a little, "Before you two go anywhere, look in the bags and grab the slippers. I do not want you walking around barefooted, understood?" he said sternly as he looked from one to the other.

John nodded quickly, while Sherlock rolled his eyes. The two went over to the bags and grabbed the slippers, "She has a good eye." Sherlock said as he pulled them out and put them on. Both pairs fitted them perfectly.

"Why do you think I hired her, she is just as smart as we are little brother." Mycroft smirked a little, as he then led the way to the kitchen.

Mycroft, with a little help from Lestrade, cooked something simple for the four of them. It didn't take them long to eat, the two kids especially as they were both hungry. Mycroft looked to them when they had finished, he could see that they were truly tired. John was yawning and almost falling asleep in his plate, while Sherlock was slumping in his seat more than normal.

"Right, wash up, teeth, then bed." He said as he picked John up and settled him on his hip. John couldn't even be bothered to protested as he leaned his head, tiredly ageist Mycroft's shoulder and began to suck his thumb, not even consciously aware that he was doing so.

Sherlock followed behind, walking along side Lestrade. He yelped a little in shock when two hands went under his arms and he was lifted into the air. He was soon placed on Lestrade's shoulder. He blinked a little, never having done this before as he hands quickly found Lestrade's and latched on.

"All right up there?" Lestrade asked as Mycroft turned to see what was going on. John giggled a little at the sight.

"Yes," he grinned as he added, "I do like the height." Causing the others to chuckled and giggled as they walked up the stairs.

They were soon in one of the bedrooms, a bathroom attached to it. Both boys were set down in the bathroom so they could prepare for bed. Mycroft was thankful for Anthea and her planning once again, as someone must have come in and prepared the room for two children. He made a mental note to give her a bonus. It didn't take long for them to finish and to be back in the bedroom, beds turned down, ready for them to climb in.

Mycroft tucked Sherlock in first, "Good night Sherlock. Oh, my room is right across the hall if you need me during the night. Lestrade's is going to be next to mine on the right. Do stay in bed Sherlock, no night time wanderings." He added as an after thought, knowing Sherlock's penchant for them when he was a child and couldn't sleep. "And no dragging John, he needs his sleep." He finished as he then went over to where John was curling up in his bed.

"Night brother," Sherlock called to him as he rolled over to face John's bed, feeling a pat on his head, he smiled up to Lestrade as he then added, "Night Lestrade."

"Night buddy." He nodded back, a soft smile on his face.

"Sleep well John, and do not hesitate to come ad get us if you need to." He told the child as he smoothed out the blankets and said softly, "Good night."

"Good nighths," John said quietly, a yawn breaking it up a little, "You'd make a good dad." He murmured as his eyes began to close.

Mycroft frowned a little at that, but then smiled. He had never really thought about having children, his job could easily be dangerous to those around him, especially those that were close. Lestrade quickly said good night to the almost asleep John and then the two of them left the room.

Mycroft shut the door quietly as they went back to the living room. The both of them needed to come up with something so that no one would be able to find out what happened to the two of them. A way to explain whom the children were, and why Sherlock and John were no longer around for a while at least. Mycroft and Lestrade just hoped it wouldn't be permanent. It was going to be a long night, for them at least.

**Thank you for reading so far, I do hope you are enjoying it. To keep up with updates on what I'm doing and how editing and writing is going for upcoming chapters, then head to the link to my tumblr in my profile.**

**And just so you know, I am already half way through a sequel to this. As soon as it is finish, I may start putting up two chapters a week for this one.**


	3. Chapter 3

**I don not own BBC Sherlock, they are the creative works of Steven Moffat, Mark Gatiss and of course the wonderful Sir Arthur Conan Doyle.**

**I do love this one, kiddie Sherlock and kiddie John are so adorable.**

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**The Science of Youth**

**Chapter Two**

Sherlock's eyes opened slowly as he began to look around the room that he was in. It was unfamiliar to him. He rolled over in the bed, now fully awake as he frowned. He saw another bed in the room. This one had a lump in the middle of it, underneath the covers. He climbed out of his bed and looked a little puzzled as the things around the room looked a lot bigger than they should have done. The young child huffed in annoyance as he realised that it wasn't a dream after all. Sherlock had hoped it had been, like any sane person would.

He walked over to the other bed and climbed up, he prodded the lump a few times, "John," he called out, waiting for his friend to wake up.

"Go 'way," came a muffled voice.

"No, wake up John," he huffed a little as he poked the lump again, this time a little bit harder.

"Pherlock, leave me be!" came a muffled yell as the covers wiggled a little bit.

Sherlock sighed as he pulled the blanket off his smaller friend, "come on John, get up, the day is wasting away."

"Pherlock," John whined a little as he uncurled a little and looked to his friend, "bugger, hoped its wath a dream." he said as soon as he saw his friends face.

"No it isn't, though I too had hoped it was as well." Sherlock said as John sat up on the bed.

"What are we going to do," John said slowly and carefully, hoping he wouldn't lisp. He grinned when he didn't, "Whats are we going fo fell peoples?" he then asked, scowling when the lisp was back.

"I don't know. Though I have no doubt that Mycroft will be able to help us come up with something to cover our absence from the public eye." he answered his friend honestly. Sherlock watched John slump where he sat. Sherlock crawled over to him and wrapped his arms around him and held him tightly. "It will all be okay you know John, Mycroft will make sure of that." he tried to reassure him.

Someone knocked on the bedroom door lightly. It opened slowly as Mycroft popped his head around the door. He smiled as he saw the two of them awake and walked in, "Good morning boys. I hope you both slept well." he smiled.

"Morning brother." Sherlock said as he looked over to him and gave him a nod, still hugging John.

"Morning Mycrofths," John smiled as he looked over to him. His head resting on Sherlock's shoulder, he looked and felt comfortable and safe.

"Right, Sherlock, why don't you go to my room and have a shower. Oh and take some clothes with you." Mycroft said as he then looked to John.

Sherlock let go of his best friend and said, "Okay," he almost jumped off the bed as he went and grabbed some of the clothes that Mycroft had brought into the room while the two boys were sleeping.

The young detective gave a smile to John and then went out of the room, towards Mycroft's bedroom. Mycroft sat down on the bed and looked down at the small boy. He knew that he was gong to have a problem with the young child. John was fiercely independent.

"Morning John, it's time for you to have a bath," Mycroft said as he picked him up and began to head for the bathroom, he grabbed clothes for the tiny doctor as he went by the dresser.

"No!" John almost yelled out, shaking his head, "I can do iths myselfss," he insisted as he began to struggle in Mycroft's arms, wanting to be put down.

"John, please stop struggling," he said in exasperation as he kept hold of the child, "I don't want to drop you."

"Mycrofths I can do iths myselfss." He insisted as he turned bright blue eyes towards the man that held him, pleading with him.

"Very well, but the door will remain unlocked and opened slightly, just in case." Mycroft bargained as he stared back at him. He knew it was a bad idea, but it would be the only way to get John to have a bath at that moment in time.

John hummed a little as he then nodded, "Okay." He could live with that.

Mycroft put John down and walked into the bathroom. He turned on the taps, to at least start it. Mycroft looked down at John as he asked him, "Would you like some bubble bath?"

John gave the man a look that said he was crazy and that he wasn't a kid, "No, thank you." He said politely.

Mycroft chuckled at the look he had been given. He knew that a childs skin was more sensitive than an adults, so he made sure that the water wasn't too hot. Mycroft was happy that a doctor would be coming over a little later on to give the two boys a check up. He wanted to make sure that the gas hadn't affected the two badly. The bath didn't take long to be ready and he helped John get in, though he protested it a little. John looked to him, a glare on his face. The look almost made Mycroft laugh, but he held it in as he walked out of the room. He stood close to the door and thought yet again on what a bad idea it was letting the child be on his own. Mycroft had a feeling though, that John would remain as independent as possible, until something happened that forced him to admit that he needed help.

Mycroft had been waiting outside the bathroom for around five minutes when he heard a cry and splashing around from the room. He rushed into the room and his eyes went wide in horror as he saw John under the water, struggling to sit back up. Mycroft quickly plucked him out of the bath and held him close. Rubbing his back and rocking his gentle as the child cried. John's thumb slowly made its way into his mouth, the young one needing the comfort that it gave him.

Mycroft held him close, rocking him gently, now running his hand through wet blond hair, hoping it would calm him down a little, and calm himself down, as his heart was hammering in his chest, "it's all right John, hush now, you're safe." he said softly.

It took a while before John's cries became slight hiccups as John finally began to calm down after his scare. He wrapped an arm around Mycroft neck and cuddle against him, sniffling a little. Mycroft grabbed the towel that was warming on the radiator and wrapped it around John. He walked into the bedroom and picked up the clothes he had chosen for the child.

"You're all right now John, safe and sound," He reassured him as he held him close, and rocked him as he sat down on the bed.

John looked to him and nodded, just humming in answer as he carried on sucking his thumb, leaning against Mycroft.

"Now you understand why I didn't want you having a bat on you own. I know that in your mind you are that of an adult. But your body is that of a young childs. One that isn't fully balance all the time, and it's dangerous, especially in a slippery bath." He told him gently as he then asked, "Would you like to try and have a bath again, but this time with me in the room?"

John just shook his head in answer, as he remained silent. He was pale and shaking a little, which was beginning to worry Mycroft a little.

"All right," he nodded as he started to dry John off, explaining, "I know that you are a very independent person and that you wish to remain that way. At the moment, that isn't possible, you're only five years old, though you appear younger. I don't mind you testing your limitations, but I want you to make sure that I, or even Lestrade is in the room with you. I don't want to see you hurt."

"I know," John said quietly as his hair was now being dried, "I'll fry nots fo flights withs you." He added softly.

Mycroft smiled at the answer as he helped him dress, "Good to hear," he said as he did the button on the jeans. Mycroft pulled the cream coloured jumper over John's head and smiled. The child looked like a mini version of his adult self.

"Fhank you," John said softly as he looked back to the floor.

Mycroft smiled and shook his head a little as he picked him up. John didn't protest, as Mycroft thought he would. Mycroft left the bedroom and headed downstairs. He had heard Lestrade and Sherlock of down them a little while ago. Mycroft knew that John had been scared badly by the incident in the bathroom as he was still sucking his thumb and clutching onto Mycroft shirt. Unconsciously trying to find some comfort.

The two walked into the large kitchen and dinning room. Sherlock and Lestrade were sitting at the table talking quietly. There was no food on the table, Mycroft had hoped that Lestrade would have made a start on breakfast, but he knew that the slightly younger man felt more like a quest than anything. Sherlock heard them enter and turned around. he smiled as he saw his friend, but it soon turned into a scowl when he saw that John was clinging to his elder brother.

"What's wrong?" he asked as he jumped from his chair and darted over to them, looking up at John.

Mycroft let the small child down as he looked to Sherlock and answered, "We had a bit of a scare in the bathroom, he went under the water for a moment, he was trying to bathe alone."

Sherlock wrapped his arms tightly around his young friend and pulled him close as he turned angry steely blue eyes onto his elder brother. Through gritted teeth he almost growled, "You should have insisted on going into the room with him and help him. No mater what he said to convince you otherwise."

"My faultss," John mumbled as he clung onto Sherlock, sniffling a little.

"I believe you should remain by my side for the rest of the day." Sherlock told him, "I don't believe I should let my brother near you, since he obviously failed in keeping you safe." He finished as he let go of John, only to take hold of his hand and lead him to the table. He helped him onto a chair and took the one next to it.

Mycroft and Lestrade shared a smile as they watched Sherlock take hold of John's hand as soon as the two were seated. Mycroft went over to the fridge and pulled out a few things, settling on French Toast for breakfast. Lestrade got up and got the kids some juice and milk, while he started to make Mycroft and himself some coffee. Mycroft didn't take that long to make breakfast, and soon the four of them were sitting around the table eating.

"How long will it take before we can return to normal?" Sherlock asked looking over to his brother. He was eating with one hand since the other was still holding John's possessively.

"That I do not know. We are still trying to locate the scientist that did this. We may have to do things the old-fashioned way, and do our own research. I have one of my top researchers coming here. He is also a doctor, so he will be examining the both of you as well. To make sure that you are both in good health and that there is nothing to worry about. And that what has happened to you is not having an adverse affect on you both." Mycroft answered him, though he could tell that it wasn't the answer his younger brother was hoping for.

"I can't just disappear. I have cases that I need to work on." Sherlock exclaimed, "So what are we going to do in the mean time?" he asked, wondering at how boring things would get without him being able to take on a new case and solve the old ones.

"I'm sorry little brother," he sighed as he looked to him, shaking his head a little.

"Well, you could always take this time to have a little fun, and to maybe have a holiday, since I know that you have never had one. I don't think that either of you have had the time to take a break since John came on the scene." Lestrade said as he looked to the small kids sitting across from him.

"Whats about phe publicss?" John wondered, as he looked to Greg, thinking it might not be that bad of an idea. It had been a hectic, adrenaline fuelled year and a bit since the doctor had meet Sherlock.

"Maybe we can say that you have a case outside of the country, somewhere like Australia?" Lestrade suggested as he thought about it a little more.

"That could work. We would have to let John be a storyteller, and make one up. Though I know he doesn't like to lie about something like that. Maybe it could be one that Mycroft has given us, as we have done one for him before and could only say that we had a case but not what it was. So when people ask us, we can say that we were working for the government." Sherlock said as he looked to his brother. "We can mention on John's blog that we are taking part in a case that we will not be able to talk about, and that we shall be incommunicado for a while until it is over."

Mycroft nodded his head in agreement, "That would work fine, if John doesn't mind writing it up for his blog and you should do the same with yours Sherlock, mention that you are going to be working with the government for an indefinite period of time, and that it will not be something that you will be able to talk about, but because of the case you will not be able to take any new cases. Make sure to mention that you will be out of contact for that time period." He said as he thought things through, he smiled to the two boys and nodded slightly.

"So, who will be the one to remain with us? I know that either of you will want to leave us alone at all." Sherlock asked as he looked between his brother and the Detective Inspector.

"I will be, I can work from my home office just as easily as I can from my work office. If I actually need to go to my office then I am sure that Detective Inspector Lestrade will be able to watch over you if need be?" he answered him as he looked over to the Inspector.

Lestrade nodded his head, "yeah, I don't mind doing that."

"Good, then that is all sorted. In about two hours Dr Connor will be arriving to see you two." Mycroft nodded as they carried on eating their breakfast.

"Oh, one thing," Greg then said as he gained the attention of everyone in the room, "Can you all call me Greg, saying my job title and last name is going to get annoying after a while," he smiled to them all.

John grinned to him; he was already calling the man by his first name, "Okay," he giggled a little causing Greg to give a slight chuckle.

"Greg?" Sherlock frowned, "I didn't know that was your given name," he added.

John had no doubt that after this was all over, that little bit of information would be deleted once again. He had noted that Sherlock had a tendency of forgetting stuff that he didn't need anymore. It could be annoying when he had to remind his friend about his work schedule.

"Very well," Mycroft smiled to him, nodding in agreement.

Greg smiled to them all, though he shook his head a little at Sherlock. He had told the Consulting Detective several times to call him Greg, and so far it hadn't happened, and Sherlock would forget once again. The four finished their breakfast and Greg stood up.

"Right, I don't know about you, but I actually have to leave here to get to work, oh and Mycroft, please thank that woman, Anthea I believe? For my clothes, though she didn't need to bring so many." Greg said as he quickly gulped down the rest of his coffee.

"That would be because you will be remaining here for the foreseeable future, I have no doubt that with these two up to their usual antics soon enough that I will require some help." Mycroft said as he looked to the man.

Greg chuckled and shook his head, "You Holmes brothers are both the same." Causing both Sherlock and Mycroft to look a little offended by the comment, "Right, see you all later then." He nodded, a smile on his face.

"Very well, I have some work to do myself, if you two can behave and be quiet, it shouldn't take me that long, a few hours at most. Then we shall be able to do something a little more amusing." Mycroft told the two children as Greg ruffled their hair and placed a kiss on the heads as he then left the room.

John and Sherlock couldn't help the giggles from what Greg had done. "Looks like he will be treating us as children no matter what." Sherlock then said as he looked to John, who nodded his head in agreement.

"Will you two behave?" Mycroft then asked them again as he waited for the two of them to answer.

"Yes, as long as there is something fun at the end of it we shall," Sherlock answered for the two of them as the younger child nodded his head in agreement.

"Yeps," John smiled as he nodded, drinking more juice as he murmured "sfills prefurs fea." the small statement caused Sherlock and Mycroft to laugh. The three soon finished their meal and Mycroft cleaned up, putting things away in the dishwasher and turning it on.

"Right, lets go to my office. I would prefer it if you are there with me, though I don't mind you being across the hall in the library. Make sure to leave the doors open if you do go. Bring a book or two with you as well if you wish." He said smiling at the two of them as they walked out of the kitchen.

The two boys still holding hands as Mycroft led the way to his office. Sherlock quickly ducked into the library and grabbed a few books for them to read. The three quickly did the blog entries for Sherlock and John's blogs. They soon settled down to work and read for a while.

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**Thank you all for the wonderful reviews, I love you all! I do hope that you are all enjoying this so far.**


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